Quaternary Ammonium Salt-Based Deep Eutectic Solvents As Alternative Base Lubricants: Interfacial Tribological...

Area of Science:

• Tribology
• Materials Science
• Green Chemistry

Background:

• Deep eutectic solvents (DESs) show promise as functional lubricants but require tailored formulation.
• Current lubrication applications often lack specific formulation design for DESs.

Purpose of the Study:

• To design and synthesize novel quaternary ammonium salt-based DESs (QAS-DL DESs) for improved lubrication.
• To investigate the structure-property relationships influencing the tribological performance of QAS-DL DESs.

Main Methods:

• Synthesis of three novel QAS-DL DESs with varying alkyl chain lengths and substituents.
• Tribological testing under a 60 N load to evaluate friction coefficient and wear rate.
• X-ray photoelectron spectroscopy (XPS) for mechanistic analysis.

Main Results:

• Increased alkyl chain length and dual-long-chain substituents significantly enhanced DES viscosity.
• The optimal high-viscosity QAS-DL DES reduced average friction coefficient by 53.7% and wear rate by 31.1% compared to ChCl-DES.
• Enhanced load-bearing capacity and interface isolation were observed with higher viscosity.

Conclusions:

• QAS-DL DESs demonstrate superior friction-reducing and anti-wear properties.
• Viscosity modulation through alkyl chain engineering is key to effective lubrication.
• Lubrication mechanism involves synergistic physical adsorption and chemical reactions forming protective tribofilms.